Closing device in an injection moulding machine for synthetic materials

ABSTRACT

The invention relates to a clamping device for an injection molding machine for plastics, including a fixed platen ( 11 ) and an end platen ( 19 ) which is connected to a moving platen ( 12 ) by means of toggle mechanism ( 13 ), wherein a hollow-shaft motor ( 7 ) with a stator ( 4 ) and a rotor ( 6 ) interacts with a spindle ( 21 ) for operating the toggle mechanism ( 13 ). It is proposed that the hollow-shaft motor ( 7 ) can be received in a recess of the end platen ( 19 ). Moreover, it is proposed that the spindle nut ( 5, 23 ) can be received in the inner dimensions of the rotor ( 6 ) of the hollow-shaft motor ( 7 ).

DESCRIPTION

[0001] The invention relates to a clamping device according to thepreamble of claim 1.

[0002] EP 0658 136 B1 discloses a clamping unit for molding tools ofinjection molding machines, including a clamping system in the form of atoggle mechanism, disposed between the moving platen and an end platen,for displacing the moving platen. Several so-called five-point togglelever systems are coupled with a common crosshead. A threaded spindle isconnected in fixed rotative engagement upon the crosshead and engages anut which is immobile in axial direction but received in the end platenfor rotation. The rotary drive is implemented by coupling the nut to ahollow shaft of an electric motor which is flange-mounted to the outsideof the end platen. The hollow shaft is internally so dimensioned as tobe suitable to easily receive the entire length of the threaded spindle,when the threaded spindle extends rearwards out of the nut. The togglelever systems are in symmetric relationship to the force axis of theclamping unit, and the threaded spindle, the spindle nut and theelectric motor with its hollow shaft are in alignment with the forceaxis of the clamping unit. A similar system is described in DE-PS 195 24314 C1.

[0003] These systems have shortcomings relating to a comparably longconstruction of the clamping device because the electric motor isarranged outside the end platen and the inner dimension of the hollowshaft is suited to the spindle length.

[0004] The invention is based on the object to provide a clamping deviceof this type, which is of significantly shorter construction while stillallowing a cost-efficient construction.

[0005] This object is realized in accordance with the invention by thefeatures of claim 1 and by the features of further independent claims 16and 17. Both solutions are hereby based on the common, basic idea toarrange as many components as possible within one another so that theirindividual axial structural lengths do not add up. The length of theclamping device is then not governed by the sum of the axial dimensionsof the individual components but by the longest one of the nestedcomponents.

[0006] As the hollow-shaft motor can be received in a recess of the endplaten, the structural length of the motor on the outer side of the endplaten is absent in comparison to the prior art. Even though a portionof the structural length of the motor extends through the inner side ofthe end platen, this is still always advantageous when the inner side ofthe end platen is constructed already with at least some space forreceiving the motor. The entire structural length of the injectionmolding machine is reduced. This reduction of the structural length ofthe injection molding machine corresponds to the thickness of the endplaten.

[0007] The subsequent claims represent advantageous improvements of theinvention.

[0008] Preferably, the recess of the end platen is configured as openingthrough the end platen. In this way, the full thickness of the endplaten can be saved as axial structural length of the clamping device.

[0009] Advantageously, the hollow-shaft motor extends hereby through theend platen. Thus, the full thickness of the end platen can be exploitedas saving of axial structural length of the clamping device.

[0010] The end platen can be configured in a geometric shape thatdeviates from the pure plate-shape. Hereby, the end platen haspreferably a back wall with a recess in which the hollow-shaft motor canbe received. In this way, the full thickness of the end platen can againbe saved when the motor is longer than the thickness of the end platen.

[0011] The greatest outer diameter of the hollow-shaft motor ispreferably smaller than the smallest inner diameter of the openingthrough the end platen. This ensures a complete fit of the hollow-shaftmotor in the opening through the end platen and a penetration of thehollow-shaft motor through the end platen.

[0012] According to an advantageous configuration of the invention, theend platen includes a preferably cylindrical recess in which thehollow-shaft motor can move into and/or move through. As a consequenceof this improvement of the invention, the structural length of theinjection molding machine is reduced in any event by the thickness ofthe end platen. The recognition to configure the end plate with acylindrical recess in which the hollow-shaft motor can move into,affords the basic idea of the invention to arrange as many components aspossible within one another so that their individual structural lengthsdo not add up, a high practical value in relation to the realization ofthe construction and enables a significant shortening of the structuralspace.

[0013] According to a preferred embodiment of the invention, the spindleis arranged in a rotationally fixed manner. The spindle end, facing themoving platen, is hereby in engagement with the rotor of thehollow-shaft motor, advantageously via a spindle nut, and the stator ofthe hollow-shaft motor is connected to the toggle mechanism. As themotor runs, it moves axially and operates the toggle mechanism. Incontrast thereto, the spindle is stationary and barely projects beyondthe outer end of the end platen. This means that the structural lengthof the injection molding machine is essentially bounded by the endplaten. The drawback of prior art injection molding machines with aclamping device driven by a spindle and a hollow-shaft motor which isflange-mounted to the outside of the end platen in accordance with theprior art, to have a structural length which is greater than aninjection molding machine with belt drive of the clamping device, isthus eliminated. The direct drive via a hollow-shaft motor and a spindleoffers, however, many advantages in comparison with a transmission withtoothed belt. This drive is safer in operation than a belt drive, whichmay fail, when the belt is ripped. The direct drive is servicefriendlier as a retensioning of the belt is eliminated. Compared to abelt drive, it is subjected to less dust because no dust can beencountered as a result of a belt drive. Moreover, it has a greaterefficiency and does not cause rolling noises of the belt. The quality ofcontrol is significantly improved compared to a belt drive in which abelt acts as elastic element. As a consequence of the high stiffness ofthe spindle drive, no hysteresis exists. The drive system is fasterbecause, despite higher mass inertia, the comparably smaller rotationspeed enables to reach the target speed faster.

[0014] According to a variation of the invention, the spindle can beguided through the end platen and secured in a rotationally fixed mannerin an anchor plate.

[0015] According to an alternative preferred embodiment of theinvention, the spindle is arranged in a rotationally fixed manner withthe rotor of the hollow-shaft motor and meshes with a spindle nut whichis connected in a rotationally fixed manner with the end platen. Thestator of the hollow-shaft motor is connected with the toggle mechanism.Compared to the first preferred embodiment of the invention, this hasthe drawback that the spindle is not rotationally fixed and stationary,but projects beyond the end platen, when the clamping device opens andthe hollow-shaft motor moves in the direction of the end platen. Thus,the advantage of a smaller structural length is lessened again. Theadvantage in relation to the first preferred embodiment of the inventionresides, however, in the fact that the hollow shaft can be directlyconnected with the spindle. As a consequence, the spindle nut, connectedto the hollow shaft and engaging the spindle, can be omitted. In view ofits great mass and its great diameter, this spindle nut has asignificant moment of inertia, and thus constitutes a higher dynamicload in comparison to a rotatable spindle. The decrease of the dynamicload in the embodiment of the invention with rotatable spindle enables aquicker movement of the clamping device. The spindle nut, which isconnected in this embodiment in a rotationally fixed manner with the endplaten, does not pose great demands as far as balancing is concerned.When especially high-quality injection molding machines are involved, inwhich the demand of space is secondary while very high dynamics shouldbe realized, this alternative embodiment of the invention is especiallyadvantageous.

[0016] In both preferred embodiments of the invention, the hollow-shaftmotor is either flange-mounted directly onto the crosshead or integratedtherein, for example, by providing the crosshead with a recess forreceiving the hollow-shaft motor. As an alternative, the stator may alsobe coupled directly to the toggle mechanism via suitable connectingelements. As a consequence of the invention, the reaction moment of thedrive and the guidance of the crosshead can be realized by a singlecost-efficient construction.

[0017] According to a further preferred embodiment of the invention, thestator of the hollow-shaft motor is connected in a rotationally fixedmanner with the end platen. The hollow-shaft motor is hereby preferablyinstalled in the recess of the end platen. The spindle is connected in arotationally fixed manner with the rotor of the hollow-shaft motor. Thearrangement has the advantage of a very small mass moment of inertia andis therefore superbly suited for a quick start-up. As the motor runs,the spindle rotates. Engaging the spindle is a spindle nut which isconnected to the toggle mechanism preferably via a crosshead. Therotating spindle moves the spindle nut axially and operates hereby thetoggle mechanism. In contrast thereto, the stator of the hollow-shaftmotor is stationary and projects barely beyond the outer end of the endplaten. This means that the structural length of the injection moldingmachine is bounded essentially by the end platen.

[0018] Based on a clamping device for an injection molding machine forplastics with a fixed platen and an end platen which is connected with amoving platen via a toggle mechanism, according to a furtherconfiguration of the general basic inventive idea to arrange as manycomponents as possible within one another so that their individual axialstructural lengths do not add up, it is proposed to provide the endplaten with a cylindrical prolongation for rotatable support of a sunwheel of an adjustment device of the end platen. The cylindricalprolongation affords the end platen with added stability. For stabilityreasons, it is therefore proposed to provide a breached end platenpreferably with such a cylindrical prolongation. In the event of aconfiguration with this cylindrical prolongation, it is suitable to useit as receptacle for a sun wheel of an adjustment device of the endplaten. A sun wheel of steel and an end platen of spherulitic cast ironprovide a good friction pair for a sliding bearing. Hereby only aminimal need for lubrication is required.

[0019] Based on a clamping device for an injection molding machine forplastics with a fixed platen and an end platen which is connected with amoving platen via a toggle mechanism, wherein a hollow-shaft motor witha stator and a rotor is provided and cooperates with a spindle foroperating the toggle mechanism, according to a further configuration ofthe general basic inventive idea to arrange as many components aspossible within one another so that their individual axial structurallengths do not add up, it is proposed that a spindle nut can be placedin the inner dimensions of the rotor of the hollow-shaft motor. Thisconstructive configuration has the advantage that the entire structurallength of the clamping device according to the invention is shortened bythe axial length of the spindle nut, as opposed to those of the priorart.

[0020] According to an advantageous configuration of the invention, thespindle nut is fixedly connected with the rotor of the hollow-shaftmotor. This is preferably implemented in the embodiments of the clampingdevice with axially movable hollow-shaft motor which is connected withthe toggle mechanism. This embodiment has the advantage of aparticularly short axial structural length of the clamping device.

[0021] According to an alternative advantageous embodiment of theinvention, the spindle nut can move into the interior space of the rotorof the hollow-shaft motor. This technique finds preferably applicationin the configuration of the clamping device in which the stator of thehollow-shaft motor is connected in a rotationally fixed manner with theend platen and the spindle nut is connected in a rotationally fixedmanner with the toggle mechanism. The spindle is here connected in arotationally fixed manner with the rotor of the hollow-shaft motor. Thisarrangement has the advantage of a very slight mass moment of inertia asthe spindle nut does not rotate, and is therefore superbly suitable fora quick start-up. The rotating spindle moves the spindle nut axially andoperates thereby the toggle mechanism. When the clamping device iscompletely opened, i.e. the toggle levers are drawn completely in thedirection of the end platen, the spindle nut plunges into thehollow-shaft motor. The entire structural length of the clamping deviceaccording to the invention is shortened in this embodiment by the axialdepth of penetration in comparison to those of the prior art.

[0022] Preferably, the configurations of the general basic inventiveides to arrange as many components as possible within one another sothat their individual axial structural lengths do not add up, arecombined. As a result, a clamping device is implemented in which thespindle nut can be received in the inner dimensions of the rotor of thehollow-shaft motor, and the hollow-shaft motor can be received in arecess of the end platen. Thus, the spindle nut, the hollow-shaft motorand the end platen can nest within one another, when the clamping deviceis open.

[0023] Exemplified embodiments of the invention are shown in thedrawings, in which:

[0024]FIG. 1 shows a cross section of a clamping device according to theinvention,

[0025]FIG. 2 shows a variation of the clamping device according to theinvention of FIG. 1 with rotatable spindle,

[0026]FIG. 3 shows a variation of the clamping device according to theinvention of FIG. 2 with rotatable spindle in which the hollow-shaftmotor is received in a cylindrical recess of the end platen.

[0027] An example of the invention is illustrated in the attachedFIG. 1. Arranged on a machine bed 16 is a fixed platen 11, whereby amovable platen 12 is able to move axially relative to the fixed platenby a toggle mechanism 13. The fixed platen 11 is connected via themachine bed 16 with an end platen 19. A spindle 21 is guided with itsend distal to the moving platen 12 through the end platen 19 and isarranged in a rotationally fixed manner in an anchor plate 3. Arrangedon the other end of the spindle 21 is a hollow-shaft motor 7 which isaxially movable on guide bars which are arranged on both sides of thespindle 21 and fixed in the end platen 19 so that they are invisible inFIG. 1. A spindle nut 5 is coupled with the hollow shaft or the rotor 6of the hollow-shaft motor 7 and is in engagement with the spindle 21.The stator 4 of the hollow-shaft motor 7 is flange-mounted to the togglemechanism 13. In this way, the functions of the crosshead and of thedrive motor are united.

[0028]FIG. 2 shows an alternative embodiment of the invention in whichthe spindle 21 is connected in a rotationally fixed manner with therotor 6 and meshes with a nut 22 which is connected in a rotationallyfixed manner to the end platen 19. The stator 4 of the hollow-shaftmotor 7 is connected to the toggle mechanism 13. The spindle 21 and thusthe hollow-shaft motor 7 moves axially as the rotor rotates. Theclamping device is opened and closed, respectively, via the togglemechanism 13. When the clamping device opens, whereby the hollow-shaftmotor 7 moves in the direction of the end platen 19, the spindle 21projects beyond the end platen 19.

[0029]FIG. 3 shows a further variation of the clamping device accordingto the invention. The hollow-shaft motor 7 is hereby received in arecess of the end platen 19. The stator 4 of the hollow-shaft motor 7 ishereby connected in a rotationally fixed manner with the end platen 19.The rotor 6 of the hollow-shaft motor 7 is connected in a rotationallyfixed manner with the spindle 21. The spindle 21 meshes with a spindlenut 23 which is connected in a rotationally fixed manner with the togglemechanism 13. Depending on the rotation direction of the motor, thespindle nut 23 moves in closing or opening direction of the clampingdevice. The clamping device is opened by fully moving the spindle nut 23back in the direction of the hollow-shaft motor 7. Finally, the spindlenut 23 plunges into the hollow-shaft motor 7. The interior space of therotor 6 of the hollow-shaft motor 7 is so configured that the spindlenut 23 can move into it. This arrangement has the advantage of a veryslight mass moment of inertia as the spindle 23 does not rotate, and istherefore superbly suitable for a quick start-up. When the clampingdevice is open, the spindle nut 23, the hollow-shaft motor 7 and the endplaten 19 are nested within one another.

[0030] Position List

[0031] Injection Molding Machine 11 fixed platen 12 moving platen 13toggle mechanism 16 machine bed 19 end platen 22 spindle nut

[0032] Drive 4 stator of the hollow-shaft motor 5 spindle nut 6 rotor ofthe hollow-shaft motor 7 hollow-shaft motor 21 spindle 23 spindle nut

1. Clamping device for an injection molding machine for plastics,comprising a fixed paten (11) and an end platen (19), which is connectedvia a toggle mechanism with a moving platen (12), wherein a hollow-shaftmotor (7) with a stator (4) and a rotor (6) interacts with a spindle(21) for operating the toggle mechanism (13), characterized in that thehollow-shaft motor (7) can be received movably or fixedly in a recess ofthe end platen (19).
 2. Clamping device according to claim 1,characterized in that the recess of the end platen (19) is configured asopening through the end platen (19).
 3. Clamping device according toclaim 1 or 2, characterized in that the hollow-shaft motor (7) extendsthrough the end platen (19).
 4. Clamping device according to one of thepreceding claims, characterized in that the end platen (19) has a backwall with a recess in which the hollow-shaft motor (7) can be receivedmovably or fixedly.
 5. Clamping device according to one of the precedingclaims, characterized in that the greatest diameter of the hollow-shaftmotor (7) is smaller than the smallest inner diameter of the openingthrough the end platen (19).
 6. Clamping device according to one of thepreceding claims, characterized in that the hollow-shaft motor (7) canmove in and/or move through the recess of the end platen (19). 7.Clamping device according to one of the preceding claims, characterizedin that the spindle (21) is arranged in a rotationally fixed manner,that the end of the spindle (21), facing the moving platen (12), is inengagement with the rotor (6) of the hollow-shaft motor (7), and thatthe stator (4) of the hollow-shaft motor is connected with the togglemechanism (13).
 8. Clamping device according to one of the precedingclaims, characterized in that the spindle (21) is guided through an endplaten (19) and secured in a rotationally fixed manner in an anchorplate (3).
 9. Clamping device according to one of the claims, 1-6characterized in that the spindle (21) is connected in a rotationallyfixed manner with the rotor (6) of the hollow-shaft motor (7) and mesheswith a spindle nut (22) which is connected in a rotationally fixedmanner with the end platen (19), and that the stator (4) of thehollow-shaft motor (7) is connected with the toggle mechanism (13). 10.Clamping device according to one of the preceding claims, characterizedin that the toggle mechanism (13) is coupled to a crosshead, and thatthe hollow-shaft motor (7) is flange-mounted to the crosshead. 11.Clamping device according to one of the claims 1-6, characterized inthat the toggle mechanism (13) is coupled to a crosshead, and that thecrosshead has a recess for receiving the hollow-shaft motor (7). 12.Clamping device according to one of the claims 1-9, characterized inthat the toggle mechanism (13) is coupled directly to the stator (4) ofthe hollow-shaft motor (7).
 13. Clamping device according to claim 12,characterized in that the stator (4) of the hollow-shaft motor (7) ismovably supported on laterally arranged guides.
 14. Clamping deviceaccording to claim 12 or 13, characterized in that the moving platen(12) is movably guided on several columns, and that the stator (4) ofthe hollow-shaft motor (7) is movably guided on one or more of thesecolumns.
 15. Clamping device according to one of the claims 1-4,characterized in that the stator (4) of the hollow-shaft motor (7) isconnected in a rotationally fixed manner with the end platen (19). 16.Clamping device for an injection molding machine for plastics,comprising a fixed paten (11) and an end platen (19), which is connectedvia a toggle mechanism with a moving platen (12), characterized in thatthe end platen (19) has a cylindrical prolongation for rotatable supportof a sun wheel of an adjustment device of the end platen (19). 17.Clamping device for an injection molding machine for plastics,comprising a fixed paten (11) and an end platen (19), which is connectedvia a toggle mechanism with a moving platen (12), wherein a hollow-shaftmotor (7) with a stator (4) and a rotor (6) interacts with a spindle(21) for operating the toggle mechanism (13), characterized in that aspindle nut (5, 23) can be received in the inner dimensions of the rotor(6) of the hollow-shaft motor (7).
 18. Clamping device according toclaim 17, characterized in that the spindle nut (5) is fixedly connectedwith the rotor (6) of the hollow-shaft motor (7).
 19. Clamping deviceaccording to claim 17, characterized in that the spindle nut (23) canmove into the interior space of the rotor (6) of the hollow-shaft motor(7).
 20. Clamping device according to one of the claims 17-19,characterized in that the hollow-shaft motor (7) can be received in arecess of the end platen (19).